Personality is often considered a factor for the choices that humans make, but what about invertebrates like spiders? NUS Biological Sciences researchers have discovered that the personality of spiders does play a part in their decision-making and hunting styles.

The biology and behaviour of these spiders are well-studied, Assoc Prof Li shared. “They have a high level of learning behaviour among invertebrates and are considered to have a very high cognitive ability,” he added. However, their personalities remain unexplored.

Published in Behavioral Ecology in December 2016, the first study focused on how personality affects the speed and accuracy of a decision in invertebrates. Decision-making typically involves a speed-accuracy trade off, meaning that a quick decision would result in a less accurate choice. The NUS team wanted to investigate if the same trade-off held true for spiders, and if their personalities determine their decisions.

The researchers first sorted the spiders between two personality types — aggressive, and docile. Each spider was then given a choice between two preferred prey items — one large, one small. “The big prey has a higher quality but they are more dangerous; the small prey does not have such a good quality but is safer,” Chia-chen explained. The more accurate choice was denoted to be the larger prey as it would have a higher pay-off.

Results of the study showed that more aggressive spiders made decisions faster, by about three to four times, but without a cost to accuracy. All the spiders chose the larger prey.

“The outcome is rather surprising, as our team had initially thought that spiders that make quick decisions are more likely to make the wrong choices, similar to humans. This new knowledge provides us with a better understanding of ecological processes like foraging and predator-prey interactions in the animal kingdom,” Assoc Prof Li elaborated.

The second study, published in January 2017 in Scientific Reports, looked at how personalities affect the foraging success of a predator. Two species of spiders were examined given its predator-prey pairing — the Portia labiata, and its common prey the Cosmophasis umbratica, which is another species of jumping spiders.

The researchers again identified the aggressive and docile Portia labiata spiders, as well as determined the behavioural predictability of the Cosmophasis umbratica spiders, by testing their reactions to a mirror and a mock predator respectively.

Different permutations of predator-prey pairs — about 70 in all, varying the behavioural predictabilities and personalities of each — were put together to determine the foraging performance of the predator. This was gauged by looking at the number of attempts the predator needed to successfully capture the prey.

“The results showed that aggressive predators fared better when catching a prey with unpredictable behaviour while docile predators performed much better when hunting a prey with predictable behaviour,” Chia-chen shared.

Explaining the significance of the two studies, Assoc Prof Li said, “Understanding personalities of spiders will shed light on how an individual animal with a particular behavioural type can improve its survivorship and reproduction.” This in turn could have implications for evolutionary theories, providing a better understanding of the nature and ecology, he added.

The study and management of animal personalities could also play a role in conservation, invasion biology and climate change.

“Some animals that are more aggressive might be less likely to escape from danger quickly. This would make it easy for poachers to kill them. More aggressive individuals are also more likely to capture prey items that they had not encountered before when they invade new environments and could also be more responsive to climate change,” he suggested.

The future will see the research team delving deeper into the personalities of spiders, studying the gene profiles of the spiders to identify the genes responsible for their personalities. They are also working on a study that expanded on the impact of personality on spiders’ decision-making, investigating their reactions to tasks of varying difficulties.